The present invention relates to a driving structure for electronic parts, which, utilizing driving force of an actuator, effects drive of a switch. The conduction state among a plurality of conductors of the switch which are arbitrarily contacted and separated with and from each other is switched over by remote control. Moreover, the actuator effects drive of a variable resistor, whose resistance is varied by moving a slider along a resistor, etc.
Hereinbelow prior art techniques will be explained, taking a switch and a variable resistor as prior art examples.
Heretofore, there is known a switch e.g. provided with a driving shaft rotated around the axial line by an actuator, a conductor plate, which is mounted on this driving shaft and rotated therewith, and a fixed plate disposed opposite to this conductor plate and supported rotatably with respect to the driving shaft, in which the conduction state between different contacts on the fixed plate is switched over by rotating the driving shaft by a predetermined amount, in a state where the rotation of the fixed plate is restricted, so that a plurality of contacts (conductors) disposed on the surface of the fixed plate and the conductor plate are selectively brought into contact.
In a switch constructed as described above, usually a rotary type motor is used as the actuator stated above.
Further a type of switches other than the rotary type of switches described above is also provided, in which the conduction state among a plurality of fixed conductors disposed separately from each other is switched over by moving a movable conductor linked with an actuator along a straight line therebetween. Also in this case, a rotary type motor is used as the actuator. The rotation of this motor is transformed into a linear movement by means of a driving mechanism to move the movable conductor described above.
Further, recently, as variable resistors used in a sliding volume, etc. in an audio device, one type is widely utilized, in which a slider is in contact with a resistor extending linearly in a conductive state and the resistance between two terminals, which are kept to be conductive through the resistor and the slider, is varied by moving the slider in the extending direction of the resistor by means of an actuator linked through the driving mechanism.
For the driving mechanism used in such a variable resistor, as described e.g. in JP-A-Sho 55-117208, there is known one, in which a rotary type motor is used as an actuator, the rotation of which is transmitted to a pulley through reduction means such as a worm gear, etc. and in this way a belt or a wire wound around the pulley stated above is forwarded so that the slider secured to the belt, etc. is moved linearly.
However, in the prior art switches described above, since a motor is used as an actuator, in order to locate a conductor such as the rotating plate, etc. at a desired position with a high precision against the inertia of the shaft of the motor, etc., it is necessary to disposed a control mechanism, which detects the rotational angle on the rotating plate, the position of the movable conductor, etc. by means of position detecting means such as a rotary encoder, a linear encoder, etc. to control the rotational angle of the motor shaft and furthermore it is necessary to disposed a stopping mechanism, which restricts the movement of the rotating plate, etc. stopped at a predetermined position. For this reason they had a drawback that the construction of the device is complicated, which causes increase in the size and the weight, which in turn raises the cost of the device.
Further they had another drawback that the motor produces electromagnetic noise, which causes erroneous operations of electronic devices or precision apparatuses, in which the switch is mounted.
Furthermore, in the prior art variable resistor described above, since a motor was used as an actuator, it had drawbacks as described below.
(1) Since the motor generates electromagnetic noise, it is necessary to take some measures against noise in order to interrupt influences of the noise on the working signal of the device (e.g. sound signal in an audio device).
(2) Since it is necessary to dispose a driving mechanism for converting the rotation of the motor into a linear movement of the slider, the construction of the whole is complicated and increases the size, which in turn causes rise in the fabrication cost.
(3) It is necessary to dispose a control mechanism to control the rotational angle of the motor shaft, in order to position the slider with a high precision to obtain a desired resistance. In this case, since the inertia of the motor shaft and various members constituting the driving mechanism acts at decelerating the motor shaft to stop it, the reponse to the control signal is bad. In addition, the resolving power is also worsened due to accumulated errors in the driving mechanism described above.
(4) Since a worm gear is used in the driving mechanism converting the rotational movement of the motor shaft into the linear movement of the slider, in the state where the slider is linked with the driving mechanism, the self-stopping action of the worm works, which inhibits manual operation of the slider. Consequently, in the case where the variable resistor is used in a device, for which manual operation is probable, such as a volume regulator in an audio device, it is necessary to dispose separately a mechanism for interrupting the linkage between the driving mechanism and the slider at need.